An algorithm for designing rings for survivable fiber networks

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World Abstracts on Microelectronlcs and Rehablhty

of surge test on high K multflayer ceramic capacitors (MLC), m which the surge current is determined by the inductance of electrical connection and a small current hmltmg resistor (0 5 ~) At a time scale less than 20 #s upon applying a voltage, V0 (0-275V), the surge current is oscillatory, with the peak current increasing with V0. The voltage across the MLC is also oscillatory with the peak voltage exceeding tw,ce v 0 The Impact of surge current, voltage, and power on relaxor and barium tltanate MLC under test is discussed Whale both types of MLC can sustain slrmlar current and power density, the failure of the relaxor MLC at a lower apphed voltage (175 V) is related to the lower breakdown strength of the relaxor dielectrics For 50-V rated MLC, the peak transient voltage should not exceed 125 V Thus both relaxor and barium tltanate MLC will perform sausfactonly under normal surge cond~tions

Defect size distribution in VLSI chips. REINHARDGLANG IEEE Trans_ Semtcond Mfg 4(4), 265 (November 1991) Very large scale Integration (VLSI) patterns consisting of parallel lines of polycrystalhne silicon have been fabricated and electrically tested for shorts The number of observed shorts was related to the line spaongs by using an analytical model for defect sensitive pattern areas_ It was found that the simple defect size distribution function h(x)= k x -n, used previously with values of n around three, projects that total number of shorts arising from a gwen defect density with reasonable accuracy However, actual defect size distributions observed microscopically are blmodal or multlmodal This comphcatlon has only a minor influence on the results projected by the model because the smaller defects are, by far, more numerous than the larger ones that make up the secondary distributions A computer program for component life estimation using multiply censored system life data. JOHN S USHER Comput, md Engng 22(I), 19 (1992) A QulckBASIC program called WEIBSYS BAS Is presented which enables the user to estimate component hfe distributions from a pooled set of muRiply-censored series-system llfe data The program yields maximum llkehhood estimates (MLEs) of Wetbull scale and shape parameters for each type of component m the system along with assocmted confidence limits It then allows the user to predict the fracUon failure expected for a new series-configuration of the components, Multilayer ceramic chip capacitors gain acceptance. TETSUJI OZAKt and SHOJt TSUeOTA JEE (Japan) 88 (September 1991). Recently multdayer ceramic chip capacitors (MLC capacators) have been mounted on main pr,nted clrcmt boards in large sets as well as on hybrid IC and clrcmts module boards MLC capacitors are representative passive surface-mounted components They are subject to the trends toward mlmaturlzat,on, higher capacitance and greater diversity to accommodate a wider range of apphcatlons_ These technological trends can be classified into five directions as shown An algorithm for designing rings for survivable fiber networks. ONDRIA J WASEM IEEE Trans. Rehab. 40(4), 428 (October 1991). The introduction of SONET technology opens opportumties for surwvable network architectures, such as self-heahng nngs, wh,ch can improve telecommumcatlon rehablhty. This paper presents an algorithm for routing fiber around a nng m a network, when the network nodes, hnks, connecttwty, and which offices are to be placed on that ring together are known. The algorithm aids automated survwable network planning The algorithm was programmed in C, and run on a SPARC-statmn Computation times on 47 examples of feasible and infeasible nngs were reasonable Overall, the average, minimum, and maximum runtlmes were 0.41 sec, 0.06 sec, and 2.93 sec, respectively Since the largest example

network used in these results, 167 offices and 240 hnks, Is the size of a typical large LATA network, the algorithm runs fast enough for the intended application In most cases, the ring routing problem cannot be solved by travehng salesman algorithms However, under certain conditions, the probiem degenerates to the travehng salesman problem, and the ring routing algorithm degenerates to the nearest neighbor method of solwng that problem

Low-temperature degradation studies of AIGaAs/GaAs modulation-doped field effect transistors. SOoN-WoN KANG and JOSEPH YA-MtN LEE Solid-St Electron 3402), 1415 (1991), The degradation of AIGaAs/GaAs modulationdoped field effect transistors (MODFETs) was studied at the low temperature of 77 K, The MODFETs were stress tested at 77 K under both short- and long-term bins stress condltlons The measured MODFET parameters include threshold 'voltage V~, transconductance gr, and the gate voltage Vu at which gin shows a maximum Shifts of V,, gm and Vu were studied as a function of stress voltage and stress time The measured shifts are found to depend on (VcVd) which indicates the influence of hot electrons coming from the high mobility channel The MODFETs were also tested for temperature cychng between 300 and 77 K up to 20 cycles Some changes of device properties at 77 K were observed Mechanical behaviour of ceramic capacitors. CHOWDARY RAMESH KORIPELLA IEEE Trans Compon Hybrids mfg Technol 14(4), 718 (December 1991) Fracture toughness, modulus of rupture, and thermal shock resistance were evaluated on COG, X7R, and Z5U type commercial ceramic capacitors with and without internal electrodes Fracture toughness was measured by precrackmg the samples followed by four point bend testing Results show that the fracture toughness values for all the dielectrics are very stmdar, close to I MPa-m ~n Relatively, COG dlelectncs are shghtly stronger followed by the X7R and Z5U dielectrics The presence of electrodes slightly increases the strength of the dielectric materials Modulus of rupture was measured by the three-point bend testing, and the results were analysed using the Welbull model Dielectric type, sample size, presence of electrodes, and the fired chip surface condltmn all affect the modulus of rupture value of the ceramic capacitor COG capacitors showed the highest strength values and X7R capacitors showed narrow distributmns in strength Thermal shock resistance measurements were made by heating the samples to different temperatures and then suddenly quenching them in water, followed by strength measurements. Critical temperature differences for fracture mltmtton for different dielectrics were determined from these results and compared with the thermal shock resistance parameters for fracture initiation (R and R') which were calculated using the measured physical and mechamcal properties of these materials Results show that the cr~t)cal temperature difference for fracture initiation is close to 125°C for 1206 size Z5U and 150°C for X7R and COG dlelectncs These values compare very well with the predicted values High mechanical reliability of back-ground GaAs 1~I chips with low thermal resistance. MASANORINISHIGUCHI,ATSUSHI NIKI, NOBORU GOTO, MITSUAKI FUJIHIRA and HIDEAKI NISHIZAWA IEEE Trans. Compon. Hybrids mfg Technol 14(4), 848 (December 1991) GaAs LSI sized 6.35mm square chips with mirror ground back surfaces (Rmax--0. I/zm) have been confirmed to be almost as highly reliable as chemically thinned ones through fracture stress experiments Two fracture strength test methods, the four-point bending test and the bs-axial tension test, were carefully performed and the data were analyzed based on Weibull statistics The 1-/zm post-gnndmg chemical etching in our